Mark Esau / Flickr, CCNorway's Global Government Pension Fund, the biggest sovereign wealth fund in the world by assets under management, is sounding a warning about the state of the British property market in the aftermath of the country's vote to leave the European Union.

The fund argues that in the immediate aftermath of the vote to leave, when assets were crashing and a mild panic gripped the markets, valuing properties in the UK became substantially more difficult. The uncertainty that remains in the UK means that valuations are still proving tricky to undertake for funds. As a result, Norway has decided to decrease the book value of its holding in UK property by 5%, the report says. Essentially, the fund now thinks its UK properties are worth 5% less than they were before the referendum.

Here's the full excerpt:

"The UK vote to leave the EU on 23 June triggered significant movements in financial markets and considerable uncertainty. It has therefore been a challenge to value unlisted properties in the UK market. The external valuers used by the fund have stated that, due to a shortage of data, they have not adjusted values in the second quarter to take account of the possible effects of the Brexit vote. The valuation of the UK real estate portfolio is therefore subject to greater uncertainty than usual. The increased volatility and uncertainty in the market are assumed to have a negative effect on property values. The fund has therefore decided to adjust down the estimated value of property investments in the UK from external valuers by 5 percent as at 30 June."

The Norwegian fund's assertion that valuing UK properties has become very difficult is somewhat reminiscent of one of the early events of the 2007-08 financial crisis when French lender BNP Paribas froze withdrawals from three investment funds after it became "impossible to value certain assets fairly regardless of their quality or credit rating."

Now obviously, the Norwegian state fund saying it became difficult to value certain assets in the UK property market is not as bad as a complete evaporation of liquidity in a huge sector of the housing market, but it is still a pretty significant development. When investors struggle to value assets properly, it can lead to all sorts of problems.

Norway's Global Government Pension Fund owns a 150-year lease on a 25 per cent stake of Regent Street in London. REUTERS/Toby Melville The freeze on redemptions occurred as investors got frightened in the aftermath of the Brexit vote, and what it could do to the UK's property market, and rushed to pull out their money from funds. The fact that fund managers could not liquidate, or sell-off, their underlying property assets fast enough to meet the demand for cash from fleeing investors was seen at the time as a potential sign that Britain might be scarily close to another financial crisis as investor confidence neared rock-bottom.

All those funds have since re-opened withdrawals as investor worries have waned somewhat, however market liquidity remains something of an issue.

As Deutsche Bank Strategist Jim Reid said in a note to clients in July: "Given the illiquidity of many other financial markets these days due to post crisis regulations this is perhaps a glimpse of what the future might hold in the next recession for other assets."

So, the "greater uncertainty" in the Norwegian portfolio of UK property may not be disastrous, but it is certainly a cause for concern if the difficulty persists.

Elsewhere in the NBIM's report, it disclosed that it holds 565 billion kroner (roughly $68.5 billion) worth of US government debt, its largest individual holding. Japanese government debt held by Norway amounts to 201 billion kroner ($24.5 billion).

It also noted that British and German stocks in its portfolio struggled in the quarter, saying: "Broken down by country, German and UK stocks made the most negative contributions to the relative return, while Spanish and Japanese stocks made the most positive contributions."